1. Field of the Invention
The invention relates to a line and a line system, and to a control method therefor, in which, for example, work is processed and is sequentially transported to any steps downstream of the processing.
2. Related Background Art
A construction of a conventional manufacturing line system will now be described with reference to FIG. 18.
A processing device unit 111 and a transport device unit 112 of a station 101 are managed by a first line controller PLC1. Similarly, a processing device unit 121 and a transport device unit 122 of a station 102 are managed by a second line controller PLC2, and a processing device unit 131 and a transport device unit 132 of a station 103 are managed by a third line controller PLC3. The first, second, and third line controllers PLC1, PLC2, and PLC3 are connected to a host computer 150 through corresponding communication lines K1 to K3, respectively. The host computer 150 collects and manages tracking data and quality data of each job or each unit or batch of work at certain timings through the first, second, and third line controllers PLC1, PLC2, and PLC3, respectively. The host computer 150 supplies the tracking data of the work to the respective equipment via the first, second, and third line controllers PLC1, PLC2, and PLC3 in accordance with a transporting state of the work (i.e., where it is), respectively.
In such conventional system construction, as the number of devices and equipment to be managed increases, higher processing ability is required for the host computer 150. The frequency of communication executed between the host computer 150 and each line controller also increases. Moreover, when the cycle time for each step of work is short, it is very difficult for the host computer 150 to manage the work step by step. Since collection of the tracking data, starting of working of the equipment, and completion signals are all responsibilities of the host computer 150, in order to preferentially transmit information, a dedicated line or the like is necessary between the host computer 150 and each line controller, and associated processing is also fairly troublesome.